Side extenders and spoilers with movable air deflectors have been used to reduce the drag on a vehicle equipped with such devices. For example, a roof spoiler on the cab of a vehicle when in an up position can assist in deflecting air over the top of a tall trailer being towed by a truck tractor. In contrast, when in a lowered position, the spoiler minimally impacts the airstream, such as when the truck is towing a flatbed trailer or no trailer at all. Similarly, side extenders have been used to deflect air outwardly for flow past the side walls of a trailer.
As another example, U.S. Pat. No. 6,846,035 to Wong et al. is understood to disclose side extenders movable from a stowed position in which the side extenders are folded toward a rear wall of a truck and a deployed position wherein the side extenders extend rearwardly and somewhat outwardly from the rear wall of the truck to deflect air past a trailer being towed. In this device, the side extenders can also be extended in length to overlay the gap between the truck tractor and trailer. The side extenders are positioned in their respective deployed and extended positions in response to the vehicle exceeding a predetermined speed. In addition, the proximity of the trailing edges of the extenders to the trailer can be reduced as the speed of the vehicle is increased.
Although aerodynamic devices exist, a need nevertheless exists for improvements in such devices and in their control.